Cleaning the screens after Permatone

Hi everyone! Not too much action here, hope someone still has some advice …

I am in bit of a trouble cleaning the screens after using Permatone inks. Though I am in trouble with the regular Jet Black Aqua as well and number of other inks but Permatone range mainly. The ink leaves a strong, coloured ghost on the screen. We have a small, clean printshop where we do our best not to use any harsh chemicals but for cleaning, we still need to use a bit. The ones we use do the work 50% of the time but when not, strong ghosts remain. Getting rid of JetBlack ghosts and most of the Permatone range is almost impossible …

Any advice ?